From 59adbf5d03f5d9380f9870e22262c59f5f9beec8 Mon Sep 17 00:00:00 2001 From: Kevin Buettner Date: Thu, 23 Aug 2018 16:00:49 -0700 Subject: [PATCH] Introduce find_function_entry_range_from_pc and use it in infrun.c An earlier version of this patch used the returned block in conjunction with BLOCK_ENTRY_PC to set stop_func_start in fill_in_stop_func() in infrun.c. While I think this was the correct thing to do, changes to find_inferior_partial_function could potentially end up with stop_func_end < stop_func_start, which is definitely wrong. For this case, we want to set both stop_func_start and stop_func_end to the start and end of the range containing the function's entry pc. I think that this functionality will be useful in many other places too - it probably ought to be used in all of the various prologue analyzers in GDB. The change to infrun.c was simple: the call to find_pc_partial_function was replaced with a call to find_function_entry_range_from_pc. The difference between these two functions is that find_pc_partial_entry_function will (potentially) return the start and end address corresponding to the range in which PC is found, but find_function_entry_range_from_pc will (again, potentially) return the start and end address of the range containing the entry pc. find_pc_partial_function has the property that *ADDRESS <= PC < *ENDADDR. This condition does not necessarily hold for the outputs of find_function_entry_range_from_pc. It should be noted that for functions which contain only a single range, the outputs of find_pc_partial_function and find_function_entry_range_from_pc are identical. I think it might happen that find_function_entry_range_from_pc will come to be used in place of many of the calls to find_pc_partial_function within GDB. Care must be taken in making this change, however, since some of this code depends on the *ADDRESS <= PC < *ENDADDR property. Finally, a note regarding the name: I had initially chosen a different name with a find_pc_partial_ prefix, but Simon suggested the current name citing the goal of eventually making naming consistent using the form find_X_from_Y. In this case X is "function_entry_range" and Y is "pc". Both the name and rationale made sense to me, so that's how it came to be. gdb/ChangeLog: * infrun.c (fill_in_stop_func): Use find_function_entry_range_from_pc in place of find_pc_partial_function. * blockframe.c (find_function_entry_range_from_pc): New function. * symtab.h (find_function_entry_range_from_pc): Declare and document. --- gdb/blockframe.c | 37 +++++++++++++++++++++++++++++++++++++ gdb/infrun.c | 7 ++++--- gdb/symtab.h | 21 ++++++++++++++++++++- 3 files changed, 61 insertions(+), 4 deletions(-) diff --git a/gdb/blockframe.c b/gdb/blockframe.c index 6ea0965..f6dd861 100644 --- a/gdb/blockframe.c +++ b/gdb/blockframe.c @@ -377,6 +377,43 @@ find_pc_partial_function (CORE_ADDR pc, const char **name, CORE_ADDR *address, /* See symtab.h. */ +bool +find_function_entry_range_from_pc (CORE_ADDR pc, const char **name, + CORE_ADDR *address, CORE_ADDR *endaddr) +{ + const struct block *block; + bool status = find_pc_partial_function (pc, name, address, endaddr, &block); + + if (status && block != nullptr && !BLOCK_CONTIGUOUS_P (block)) + { + CORE_ADDR entry_pc = BLOCK_ENTRY_PC (block); + + for (int i = 0; i < BLOCK_NRANGES (block); i++) + { + if (BLOCK_RANGE_START (block, i) <= entry_pc + && entry_pc < BLOCK_RANGE_END (block, i)) + { + if (address != nullptr) + *address = BLOCK_RANGE_START (block, i); + + if (endaddr != nullptr) + *endaddr = BLOCK_RANGE_END (block, i); + + return status; + } + } + + /* It's an internal error if we exit the above loop without finding + the range. */ + internal_error (__FILE__, __LINE__, + _("Entry block not found in find_function_entry_range_from_pc")); + } + + return status; +} + +/* See symtab.h. */ + struct type * find_function_type (CORE_ADDR pc) { diff --git a/gdb/infrun.c b/gdb/infrun.c index b25d745..7731ccd 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -4287,9 +4287,10 @@ fill_in_stop_func (struct gdbarch *gdbarch, { /* Don't care about return value; stop_func_start and stop_func_name will both be 0 if it doesn't work. */ - find_pc_partial_function (ecs->event_thread->suspend.stop_pc, - &ecs->stop_func_name, - &ecs->stop_func_start, &ecs->stop_func_end); + find_function_entry_range_from_pc (ecs->event_thread->suspend.stop_pc, + &ecs->stop_func_name, + &ecs->stop_func_start, + &ecs->stop_func_end); ecs->stop_func_start += gdbarch_deprecated_function_start_offset (gdbarch); diff --git a/gdb/symtab.h b/gdb/symtab.h index 746b5e6..eb14f34 100644 --- a/gdb/symtab.h +++ b/gdb/symtab.h @@ -1725,12 +1725,31 @@ extern struct symbol *find_symbol_at_address (CORE_ADDR); This might suggest that *ADDRESS and *ENDADDR ought to be set to the limits of the entry pc range, but that will cause the *ADDRESS <= PC < *ENDADDR condition to be violated; many of the - callers of find_pc_partial_function expect this condition to hold. */ + callers of find_pc_partial_function expect this condition to hold. + + Callers which require the start and/or end addresses for the range + containing the entry pc should instead call + find_function_entry_range_from_pc. */ extern int find_pc_partial_function (CORE_ADDR pc, const char **name, CORE_ADDR *address, CORE_ADDR *endaddr, const struct block **block = nullptr); +/* Like find_pc_partial_function, above, but *ADDRESS and *ENDADDR are + set to start and end addresses of the range containing the entry pc. + + Note that it is not necessarily the case that (for non-NULL ADDRESS + and ENDADDR arguments) the *ADDRESS <= PC < *ENDADDR condition will + hold. + + See comment for find_pc_partial_function, above, for further + explanation. */ + +extern bool find_function_entry_range_from_pc (CORE_ADDR pc, + const char **name, + CORE_ADDR *address, + CORE_ADDR *endaddr); + /* Return the type of a function with its first instruction exactly at the PC address. Return NULL otherwise. */ -- 2.7.4